Dear Practo user,
It is a very common problem nowadays as lot of information is available online, although not always authentic. This leads to problems like these which are bring experienced by your relative as well.
It could simply be health anxiety, but can also be a feature of some other related psychological problem which needs to be assessed after collecting detailed case history.
Next Steps
Ask your relative to consult a Clinical Psychologist in person for proper assessment of the condition and subsequent psychological intervention.
Hope this helps. Best wishes.